Oscillating circuits applied to electrical musical instruments and the like



June 9, 1931. J. BETHENOD 1,309,503

DSCILLATING CIRCUITS APPLIED 1'0 ELECTRICAL MUSICAL INSTRUMENTS AND THE LIKE Filed lay 20. 1929 Ta Ze radz wer Patented June 9, 1931 JOSEPH BETHEIIOD, OE PARIS, FRANCE OSCILLATING- CIRCUITS APPLIED TO ELECTRICAL MUSICAL INSTRUMENTS AND THE LIKE Application filed May 20, 1929, Serial No. 364,633, and in France May 31, 1928.

The present invention relates to improvements in electrical musical instruments, that is to say those in Which the sound is produced by loud speakers supplied, preferably through thermionic amplifiers, from a source of alternating electric current of audinote produced, or to produce from the same sourcedifferent notes of Wh1ch the relative pitch varies according to ratios correspond- 1ng to the series of Whole numbers. I

The inventlon consists broadly in connecting to the source a line artificially loaded of relatively very low value.

as may be convenient. The extremity of this line may be connected across an impedance of arbitrary character, chosen according to the effect to be produced. The value of this impedance may vary from zero (line short circuited) up to infinity (line on open circuit). As a non-limitative example, one may take the case of a line on open circuit connected to the source through an impedance The circuit Will be resonant in known manner to frequencies of which the relative pitch varies nearly according to ratios of the series of odd numbers: 1, 3, 5, 7 From the terminals, of a suitable element included in the circuit so formed an alternating potential of complex form'may then be taken ofi, either in its entirety to supply a thermionic amplifier, or only in part, the frequencies not made use of being excluded by a filter of a nature dependent onthe particular case. This filter may for example be formed by an intermediate oscillating circuit tuned to the frequency it is desired to trap. The invention Will be better understood With the help of the accompanying figure, which gives schematically and for the sake of example one arrangement according to the invention.

In this figure, the source 1 supplies an artificially loaded line 2, represented conventionally by a series of self inductances 3 and" condensers 4. This line is closed across an impedance Z, designated by 5. The Winding of the transformer 6 is included in the circuit," and from its terminals an alternatingpoten tial of complex form containing harmonics may be taken olf, Whichis transmitted to the oscillating circuit 7 The oscillatory circuit 7 may contain, as previously explained, an amplifier which is preferably preceded by a filter. lating circuit is however immaterial.

My system which employs an output cir cuit element connected in series in the line corresponds to a constant current system such as a current transformer or series motor. In a system such as here disclosed, a constant current system presents a-decided advantage over. a constant voltage system, since in the The exact arrangement of the oscil-' constant current system it is possible-tomodeasily adjusted control. Thischaracteristic makes possible the utilization of theconstant current arrangement in electrical musical instruments.

ify the series of amplified harmonics by an If the artificial line is open at its terminating impedance Z, the circuit is resonant on all the odd harmonics like a pipe open onone end and. closed on the other end. If

the'terminating impedance Z is short circuited, the circuit is resonant on all the even harmonics, like a pipe closed at both ends.

of certain harmonics in a. selective manner.

By varying the output impedance Z, it is possible to find a value for Which the am- I plified harmonics Wlllbe those Which are de-' sired. This result cannot be obtained in a constant voltage system.

It is obvious that in accordance with these principles many variations are possible all conforming to the spirit of the invention. The invention may be extended to frequencies outside the audible range.

IVllat I claim and desire to secure by Letters Patent is 1- 1. In an electrical musical instrument, a source generating an alternating current containing a fundamental and its harmonics, an artificial line supplied by said source, a shunt impedance terminating said artificial line, at least one circuit element inserted in series in a conductor of said line, and means for trans mitting the potential difference delivered at the terminals of said circuit element to locations remote from said source.

2. In an electrical musical instrument, a source generating an alternating current containing a fundamental and its harmonics, an artificial line supplied by said source, a variable shunt impedance terminating said artificial line, at least one circuit element insorted in series in a conductor of said line, and means for transmitting the potential difference delivered at the terminals of said circuitelement to locations remote from said source.

3. In an electrical musical instrument, a source generating an alternating current containing a fundamental and its harmonics, an artificial line comprising series inductances and shunt capacities supplied by said source, a variable shunt impedance terminating said artificial line, at least one circuit element inserted in series in a conductor of said line, and means for transmitting the potential difference delivered'at the terminals of said circuit element to locations remote from said source.

4. In an electrical musical instrument, a source generating an alternating current containing a fundamental and its harmonics, an artificial line comprising a network of inductances and capacities supplied by said source, a variable shunt impedance terminating said artificial line, at least one circuit element inserted in series in a conductor of said line, and means for transmitting the potential difference delivered at the terminals of said circuit element to locations remote from said source.

5. In an electrical system for generating.

musical sounds, a source of alternating current having a fundamental and its harmonics, an artificial line comprising a net of inductances and capacities and a terminal impedance, a circuit element connected in series in said transmission line, and an output circuit in electrical relation With said series circuit element, said artificial line being resonant to the fundamental of said source of alternating current and certain of its harmonics. 

